Field of the Invention
The present invention relates to a radiation imaging apparatus and a radiation imaging system.
Description of the Related Art
A detection apparatus constituted by combining a conversion element that converts radiation into charges, a switching element such as a thin-film transistor, a pixel array in which wiring lines are provided, a driving circuit, and a readout circuit is widely used as a radiation detection apparatus. Recently, multi-functionality of such a detection apparatus is being examined. As one of these functions, it is examined that the detection apparatus incorporates a function of detecting and measuring information about irradiation by the detection apparatus while a radiation source emits radiation. For example, the timing to start irradiation with radiation from the radiation source is detected, and the radiation dose or the integrated irradiation amount is measured. This function also makes it possible to monitor the integrated amount of the dose, and when the integrated amount reaches a predetermined amount, control the radiation source by the detection apparatus, and end the irradiation.
A wiring line for reading out a detection signal from a detection element that detects radiation is wired through a given region of pixels for image formation up to a readout circuit outside the pixels. Measurement of the radiation dose needs to be performed in real time during radiation irradiation. That is, the dose needs to be measured while the pixels for image formation are irradiated with radiation and the potentials of the electrodes of the pixels vary at any time upon the radiation irradiation. For this reason, crosstalk is generated by capacitive coupling between the wiring line for reading out a detection signal and the electrode of the pixel for image formation, and influences quantitative measurement of the radiation dose, resulting in poor measurement accuracy.
Japanese Patent Laid-Open No. 2012-52896 discloses an arrangement in which a sensor for detecting radiation is incorporated in a pixel array in order to detect the timing to start irradiation with radiation, and a signal from the sensor is read via a wiring line connected to the sensor. This patent literature discloses that the influence of noise superposed on the wiring line is suppressed by calculating a difference between electrical signals respectively generated on a signal line connected to the sensor and a signal line not connected to the sensor.
In the above-mentioned patent literature, the signal line connected to the sensor and the signal line not connected to the sensor are provided, so extra signal lines are added. Also, an input circuit for processing a signal is also required in accordance with a signal.